Many times it is quoted that the next World War will be fought over water. It is also a fact that in future fresh and potable water will be one of the most precious resources for society. With the rapid increase in population of the world, the requirement of clean water will increase exponentially. This clean water is required for municipal purpose, and agricultural and industrial activities.
On an average, there is sufficient clean water for everybody. However, this water is distributed unevenly in the world. On the one hand, Canada, Russia, Brazil, and USA have 80181 m3, 29981 m3, 27221 m3, 8845 m3 of water per person per year respectively, while the countries like China, India, Pakistan, Sudan and Israel have 2061 m3, 1171 m3, 296 m3, 101 m3, 91 m3 of water per person per year respectively. Within a particular country also there is an unequal distribution of water among the areas. In India, water is abundant in Ganga and Brahmaputra basin while there is water scarcity in parts of Rajasthan, Gujrat, Maharashtra and even in parts of Karnataka and Odisha. It is proposed in some studies that in Rajasthan, water availability may drop up to 450 m3 by 2050.
Scarcity of water can be divided into two categories. First category of water scarcity involves insufficient water for agriculture. There is huge gap between demand and supply for this component in water scare areas. The second category of water scarcity involves insufficient water supply for municipal and industrial needs. In many locations, the number of available water resources are fixed, unlike the constantly increasing population, ultimately catalysing water scarcity.
Some methods suggested by scientists and researchers to solve the water scarcity problem are rain water harvesting, water reuse, artificial rain and other water conservation practices. Every method has its advantages and disadvantages. Recently, artificial rain and cloud seeding is attracting the attention of researchers. Artificial rain or cloud seeding is a type of weather modification that aims to change the amount or type of precipitation that falls from clouds by dispersing some chemical substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical processes within the cloud. The most common chemicals used for cloud seeding include silver iodide, potassium iodide and dry ice (solid CO2). The availability of suitable type of clouds is a major challenge for artificial rain. The suitable method for launching the chemicals and the economics of the whole process is also a major challenge. Till now the general approach is that cloud seeding is used only when there is drought in a particular area or there is pollution affecting the quality of life of inhabitants of a city. It will give minimum rainfall in that area so that pollutants will settle down on earth. In other areas it will give minimum potable water so that municipal water demand can be fulfilled.
One major point of concern is the type of areas on the basis of cloud availability and rainfall patterns. The clouds vary from many to almost nil in the different regions. When there are no clouds or excess rainfall, there is no point for artificial rain or cloud seeding. It is beneficial to use this technique in the areas where there is a sufficient average rainfall. If this technique is used for those areas, it will increase the total rainfall in that region. For example, the Malwa region of Madhya Pradesh (Indore, Ujjain, Mandsaur) and Mewar region of Rajasthan (Udiapur, Chittorgarh and Rajsamand) observe average rainfall ranging between 700 and 900 mm per year. There are some major reservoirs in these basins for irrigation and municipal purposes viz., Gandhi Sagar, Rana Pratap Sagar on Chambal River and Bisalpur Dam on Banas River. Due to various regions, some of these reservoirs were not filled up to their full capacity. If by cloud seeding the total rainfall in that region can be increased, it will increase the possibility of increase in water level in the reservoirs and finally the overall water availability in the command area and downstream of the reservoir. This will also increase the water in the lakes and ponds in the major cities and more water for rain water harvesting.
Use of artificial rainfall in the areas of average rainfall as much as in the drought zone and during drought will be instrumental in availing sufficient water for irrigation and municipal purposes.
Dr Kedar Sharma, Institute of Engineering, JKLU